Cabinet members from four Republican administrations Wednesday made a plea for federal action to address climate change, citing new evidence that public opinion is shifting in favor of it.

The officials, all former heads of the Environmental Protection Agency, said there is a sizable faction within the Republican Party that would support climate action, but only if they’re backed by vocal public support.

“There are a lot of Republicans that do believe that the climate is changing and humans play a role in that,” said Christine Todd Whitman, who led EPA under President George W. Bush. “They just need some cover. And if they hear from the public that this is an issue of importance to them … you’re going to find more and more of them speaking out.”

Whitman was one of four Republican EPA chiefs to testify this morning before the Senate Environment and Public Works Committee, joined by William D. Ruckelshaus (who served under Presidents Nixon and Reagan), Lee M. Thomas (Reagan), and William K. Reilly (George H.W. Bush).

The current Republican Party line casts skepticism on the science linking human activity to global warming and staunchly opposes legislative or administrative carbon caps.

But in a roundtable with reporters, all four former officials reiterated the need for action on climate change, regardless of the political situation in Congress. And, citing an NBC News/Wall Street Journal poll that found 61 percent of Americans back action to combat climate change, they predicted the political dam would break.

“When all of these environmental issues have been addressed successfully in the past, it’s where there’s strong public support for action,” said Ruckelshaus, who was the first head of EPA, under Nixon. “That [poll] is indicative of what seems to be a shift in public opinion on that, and if that turns into a demand for action, something will happen.”

Ruckelshaus said that was the situation Nixon faced before he created EPA in 1970. Even though the president hadn’t entered the White House with the environment atop his agenda, he was “clearly moved by public opinion” that showed Americans wanted to clean up their water and air.

While Whitman said Congress was the “preferable vehicle by which to make things happen,” she praised President Obama for moving to regulate carbon dioxide from power plants unilaterally.

For more evidence of momentum, all four pointed to work being done at the local and state levels. The flexibility under the power-plant rule that will allow states to look to cap-and-trade programs, clean energy, and other methods to meet emissions goals would help move that forward, Reilly said.

“Leadership in those states that take it will show the way for the country as a whole and for other states that it’s possible to do that without shutting the economy down or making everyone so mad you can’t function,” he said. “It’s just not true that if you shift your attention from resisting the rule to trying to figure out ways tot make it work, then we’ll all make a lot of progress.”

Whether the message from the retired administrators reaches the less politically shielded legislators remains to be seen. Some lawmakers’ opening statements at the hearing—where dozens of coal miners filled chairs in the audience to protest the climate plan—had a familiar ring.

“Recently, many of the extreme weather claims being made were found to be without merit,” said ranking member David Vitter of Louisiana. “What has come true is the economic calamity that befalls nations that head down the path President Obama unilaterally selected for America.”